JP6925208B2 - Method for producing silicon carbide single crystal - Google Patents

Description

The present invention relates to a method for growing a silicon carbide single crystal by a sublimation recrystallization method using a seed crystal.

A sublimation recrystallization method is known as one of the methods for producing a silicon carbide single crystal. This sublimation recrystallization method is a method of growing a single crystal of silicon carbide from a seed crystal by sublimating a sublimation raw material powder at a high temperature to generate a sublimation gas and supplying the sublimation gas to a seed crystal portion.

As a heating method, a method of heating a crucible by using high-frequency induction heating and heating the sublimation raw material filled in the crucible by heat transfer from the generated crucible is common. In such a method, strong heat is generated near the crucible wall and heat is transferred to the silicon carbide raw material, so that a temperature gradient is generated in the sublimation raw material of the raw material filling portion depending on the shape of the crucible. Due to this temperature gradient, the amount of raw material sublimation gas produced is distributed, and the raw material is less likely to sublimate in the low temperature portion than in the high temperature portion.

When a crucible having a cylindrical inner side wall is filled with a silicon carbide raw material, the raw material portion in contact with the crucible side wall is heated more strongly than the raw material near the central axis of the crucible. In particular, when aiming to increase the size of the ingot, it is necessary to use a crucible having a larger diameter, and it is necessary to fill a large amount of silicon carbide raw material in order to supply a large amount of raw material sublimation gas. In this case, the temperature gradient in the raw material of the raw material filling portion becomes larger, and it becomes difficult to efficiently sublimate the raw material.

Therefore, it has been proposed to make various improvements to the crucible structure in order to reduce the temperature gradient in the raw material of the raw material filling portion and improve the sublimation efficiency of the raw material.
For example, a manufacturing method for efficiently sublimating a raw material near the central axis of a crucible is disclosed by using a crucible structure in which a graphite member that becomes a part of a crystal growth container supported near the center of the bottom surface of the raw material filling portion is used. (Patent Document 1). Further, a manufacturing method for efficiently heating the central portion by fixing a disk-shaped graphite partition wall to the wall surface of the crucible is disclosed (Patent Document 2).

In addition, a method of controlling the temperature of the raw material in the raw material filling portion by introducing a member having a specific thermal conductivity above the raw material filling portion has also been proposed.
For example, by arranging a heat insulating material on the upper part of the raw material filling part, the heat flow generated from the upper surface of the raw material center part toward the seed crystal side is blocked, and the temperature difference between the raw material center part and the peripheral part is reduced, so that the raw material is efficiently used. A manufacturing method for heating a central portion is disclosed (Patent Document 3). Further, a manufacturing method of arranging a heat equalizing member having high thermal conductivity on the surface of a raw material including a radial center portion of a crucible is also disclosed (Patent Document 4).

Japanese Unexamined Patent Publication No. 5-587774 JP-A-2017-56969 Japanese Unexamined Patent Publication No. 2015-212207 Japanese Unexamined Patent Publication No. 2006-69851

In order to efficiently sublimate the silicon carbide raw material, it is necessary to sufficiently heat the vicinity of the central axis of the raw material filling portion.
Generally, in order to sufficiently heat the raw material filled in the raw material filling portion, it is necessary to raise the temperature of the side wall portion of the crucible. On the other hand, if the temperature of the side wall portion of the crucible is increased, the temperature of the entire crucible is increased and the crystal temperature during growth is also increased, which makes it difficult to sufficiently grow the crystals.

When the above-mentioned conventional method and apparatus for producing a silicon carbide single crystal are used, the technique disclosed in Patent Document 1 still has a problem that the vicinity of the central axis still needs to be sufficiently heated, and the large diameter of the single crystal remains. It is difficult to efficiently heat the raw material near the central axis of a crucible with a large diameter due to the conversion. In addition, since the heat transfer member is introduced as a part of the crucible, the degree of freedom of the shape is small and it is difficult to control.

In the technique disclosed in Patent Document 2, since a disk-shaped member having an opening in contact with the wall surface of the crucible is provided, a large amount of rising flow of sublimation gas generated near the wall surface of the crucible, which is strongly heated, is a member. There is a problem that it is hindered by. This effect becomes remarkable when a crucible with a large diameter is used to increase the diameter of a single crystal, and there arises a problem that the supply of sublimation gas from the raw materials near the central axis of the crucible and the wall surface cannot be compatible. Further, in the techniques disclosed in Patent Documents 3 and 4, since the member is introduced on the surface of the raw material near the central axis of the crucible, the flow to the upper part near the central portion is restricted, and the diameter of the single crystal is increased. When a crucible with a large diameter is used, it is difficult to secure a sufficient amount of sublimation near the central axis.

From the above, it is difficult to sufficiently sublimate the raw material near the central axis of the crucible when a crucible having a large diameter is used by the methods disclosed in Patent Documents 1 to 4.

The present invention has been made in view of the above problems, and even when a crucible having a large diameter is used, the raw material near the center of the crucible is sufficiently heated without suppressing the supply of sublimation gas from the raw material near the wall surface. It is an object of the present invention to provide a method for producing a silicon carbide single crystal capable of efficiently sublimating a raw material.

In the production of a silicon carbide single crystal by the sublimation recrystallization method using a crucible having a large diameter, the present inventors use the silicon carbide raw material (hereinafter, may be simply referred to as a raw material) filled in the raw material filling portion of the crucible for efficiency. I examined how to sublimate well. As a result, by arranging a heat transfer member having a specific shape at a specific position inside the silicon carbide raw material filled in the raw material filling portion, it is possible to efficiently produce a large-diameter and long silicon carbide single crystal. We found what we could do and came to complete the present invention.
That is, the present invention provides the following means for solving the above problems.

[1] A single crystal growth apparatus having a graphite-made pit body, a raw material filling portion located at the lower part of the pit body, and a seed crystal setting portion in which a seed crystal is installed at a position facing the raw material filling portion is used. Then, the sublimation gas generated by heating the silicon carbide raw material filled in the raw material filling part is recrystallized on the silicon carbide seed crystal installed in the seed crystal installation part, and the silicon carbide single crystal by the sublimation recrystallization method is performed. It is a manufacturing method of
The crucible body has a cylindrical inner wall surface and has a cylindrical inner wall surface.
An annular heat transfer member made of a substance having a higher thermal conductivity than the silicon carbide raw material is arranged inside the silicon carbide raw material.
A method for producing a silicon carbide single crystal, wherein the heat transfer member is arranged in a region where the distance from the central axis of the crucible body is 5 mm or more and 0.85 times or less the inner radius of the crucible body. ..
[2] The method for producing a silicon carbide single crystal according to 1 above, wherein the heat transfer member has a thermal conductivity of 30 W / mK or more at a temperature of 2000 ° C. or higher.
[3] The method for producing a silicon carbide single crystal according to 2 above, wherein the heat transfer member is made of graphite or tungsten.
[4] The shape of the heat transfer member is axisymmetric, and the heat transfer member is arranged so that the central axis of the heat transfer member coincides with the central axis of the crucible body. The method for producing a silicon carbide single crystal according to item 1.
[5] The method for producing a silicon carbide single crystal according to 4 above, wherein the heat transfer member has a cylindrical shape, a perforated disk shape, or an annular shape.
[6] The method for producing a silicon carbide single crystal according to 4 to 5, wherein a plurality of the heat transfer members are arranged inside the silicon carbide raw material.

According to the method for producing a silicon carbide single crystal of the present invention, when producing a large-diameter and long silicon carbide single crystal, the silicon carbide raw material filled in the crucible is a raw material near the side wall of the crucible, which tends to be hot. Since the raw material near the central axis of the crucible is efficiently heated while ensuring the use of the raw material, the raw material can be efficiently sublimated.

It is sectional drawing of the single crystal growth apparatus (Example 1) used in the manufacturing method of the silicon carbide single crystal of this invention. It is a figure which shows the simulation result of the porosity in the raw material in a raw material filling part after crystal growth for 50 hours in Example 1. FIG. It is a figure which shows the simulation result of the porosity in the raw material in a raw material filling part after crystal growth for 50 hours in a conventional method. It is sectional drawing which shows the structure in the crucible of Example 4. FIG. It is sectional drawing which shows the structure in the crucible of Example 5. FIG. It is sectional drawing which shows the structure in the crucible of Example 6. It is a figure which shows the increase rate of the raw material sublimation amount when the position and shape in the horizontal direction of a heat transfer member are changed.

Hereinafter, a method for producing a silicon carbide single crystal according to an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. The drawings used in the following description may be enlarged for convenience in order to make the features of the present invention easy to understand, and the dimensional ratios of each component may differ from the actual ones. .. The materials, dimensions, etc. exemplified in the following description are examples, and the present invention is not limited thereto, and the present invention can be appropriately modified without changing the gist thereof.

In the method for producing a silicon carbide single crystal according to an embodiment of the present invention, a graphite crucible body, a raw material filling portion located at the lower part of the crucible main body, and a seed crystal are installed at positions facing the raw material filling portion. A single crystal growth device having a seed crystal support is used.
Single crystal growth is a recrystallization in which a sublimation gas generated by heating a silicon carbide raw material (silicon carbide powder) filled in a raw material filling portion is recrystallized on a silicon carbide seed crystal installed in the seed crystal setting portion. It is carried out by the crystallization method.
Here, an annular heat transfer member made of a substance having a higher thermal conductivity than the silicon carbide raw material is arranged inside the silicon carbide raw material, and the temperature distribution of the silicon carbide raw material in the raw material filling portion can be made uniform.

[Silicon Carbide Single Crystal Growth Device]
First, the silicon carbide single crystal growth apparatus used in the present invention will be described. FIG. 1 is a schematic cross-sectional view of the entire silicon carbide single crystal growth apparatus used in the present invention.

The silicon carbide single crystal growth apparatus shown in FIG. 1 includes a cylindrical crucible body 1 made of graphite, a raw material filling section 2 in which a silicon carbide raw material 8 for sublimation located at the lower part of the crucible body is filled, and a raw material filling section 2. A seed crystal support portion 3 in which a seed crystal is installed at a position facing the surface, a graphite heat insulating material 4 installed so as to surround the crucible body 1, and the crucible body functioning as a heat generating member outside the heat insulating material 4. A work coil 5 for high-frequency induction heating for generating heat of 1 is provided.
Further, when single crystal growth is performed using the single crystal growth apparatus, a seed crystal 6 made of a silicon carbide single crystal is installed in the seed crystal support portion 3, and the raw material filling portion 2 is filled with the silicon carbide raw material 8. A heat transfer member 7 is arranged inside the silicon carbide raw material 8 to efficiently transfer the heat generated by the work coil 5 from the crucible body 1 to the central region of the raw material filling portion.

[Heat transfer member]
Since the heat transfer member 7 is arranged for the purpose of improving the heat conduction inside the raw material filling portion 2, the heat transfer member 7 has a heat higher than the thermal conductivity (25 W / mK) of silicon carbide at a temperature of at least 2000 ° C. or higher. Must have conductivity. Further, the thermal conductivity of the heat transfer member 7 is preferably 30 W / mK or more, more preferably 40 W / mK or more, and even more preferably 50 W / mK or more at 2000 ° C. or higher.

Further, since the heat transfer member 7 needs to be stable even in a high temperature region, it is preferably made of graphite or tungsten having a high melting point.

The shape of the heat transfer member 7 is annular so as not to obstruct the flow of the sublimation gas generated inside the raw material filling portion 2 during the growth of the silicon carbide single crystal. As used herein, the term "annular" means a shape having an opening (penetration portion) in a portion including the center. Further, the shape of the heat transfer member 7 is preferably an axially symmetric annular shape. When the shape of the heat transfer member 7 is axisymmetric, it is preferable to arrange the heat transfer member 7 so that the central axis of the heat transfer member 7 coincides with the central axis of the crucible body 1.

Further, among the axisymmetric annular shapes, a cylindrical shape, a perforated disc shape, or an annular shape is more preferable. In the present specification, when an axially symmetric annular shape is cut along a plane passing through the central axis, a shape having a rectangular cross section and a length in the axial direction that is longer than the length in the radial direction is referred to as a cylinder. A shape with a rectangular cross section and a long radial length is called a perforated disk shape, a shape with a circular cross section is called an annular shape, and a shape with an elliptical cross section is called an annular shape. do.
Since the cylindrical and perforated disk-shaped heat transfer members occupy a small volume with respect to the surface area, the volume of the heat transfer members can be reduced as compared with other shapes in order to obtain the same heat transfer effect, and the raw material. It is preferable in that the amount of the raw material to be filled in the filling portion can be increased. Further, the annular shape and the annular shape are preferable because they occupy a large volume with respect to the surface area, but the shape has no corners and the flow of the sublimation gas is not easily obstructed.

Further, in the case of the cylindrical shape and the perforated disk shape, when the central axis is aligned with the central axis of the crucible main body 1 and arranged in the crucible main body 1 (raw material filling portion 2), the inner wall surface or the bottom surface of the crucible main body 1 is formed. The shape may have surfaces that are not parallel to each other, and can be freely designed as long as it is axisymmetric with respect to the central axis of the crucible body 1. Regarding the volume of the heat transfer member 7, if the member is too small, the effect of improving the efficiency of heat transfer in the raw material filling portion cannot be obtained and it is considered that there is a problem in strength. And in the case of a shape similar to them, the length of the shortest side of the heat transfer member is preferably 1 mm or more, and in the case of an annular shape or a similar shape, the diameter of the cross section is preferably 1 mm or more.

The heat transfer member 7 is arranged inside the raw material filling portion 2 at a position not in contact with the inner side wall of the crucible main body 1. The position of the heat transfer member 7 depends on its shape, but is a region where the distance from the central axis of the crucible body 1 is 5 mm or more and 0.85 times or less of the inner radius (half the inner diameter) of the crucible body 1. Placed inside. Further, it is preferable that the heat transfer member 7 is arranged in a region where the distance from the central axis of the crucible body 1 is 10 mm or more and 0.75 times or less the inner radius of the crucible body 1.

The heat transfer member 7 is installed inside the raw material 8 so that it can exert an effect on the raw material in the upper part near the central axis of the crucible body 1 of the raw material filling portion 2 which is the most difficult to heat during single crystal growth, that is, the raw material 8 It is placed in a position that is not exposed from the surface of the.

The heat transfer member 7 may be arranged so as to be in contact with the bottom surface of the pit body 1, but since the structure needs to transfer heat to the upper part of the raw material filling portion, and if the volume of the heat transfer member 7 is too large, Since the amount of raw material that can be filled in the raw material filling portion 2 is limited, it is preferable that the raw material is arranged in a region where the distance from the bottom surface of the pit body 1 is 0.25 times or more the raw material filling height.

A plurality of heat transfer members 7 may be arranged inside the raw material 8. For example, as shown in FIG. 6, a cylindrical heat transfer member 7a and a heat transfer member having an outer radius (half the outer diameter) smaller than the inner radius (half the inner diameter) of the heat transfer member 7a. Even if the member 7b is arranged in the raw material so that the central axes of the two heat transfer members are aligned with the central axis of the radius body, that is, the two heat transfer members are concentric when viewed from above. good.
Further, a plurality of perforated disk-shaped heat transfer members may be arranged side by side in the vertical direction so that their central axes coincide with the central axes of the crucible body.
Further, a plurality of heat transfer members having different structures (cross-sectional shapes) may be arranged at different positions in the horizontal plane without being in contact with each other.
As a method of arranging the heat transfer member inside the raw material filled in the raw material filling portion, for example, the raw material is filled to a predetermined height 1 of the raw material filling portion, the heat transfer member is placed on the surface of the raw material, and then the heat transfer member is placed. A method of filling the raw material up to a predetermined height 2 again can be mentioned, but the method is not limited thereto.

Examples and comparative examples of the present invention will be shown below, and the present invention will be described in more detail. It should be noted that these are merely examples for explanation, and the present invention is not limited thereto.

In the examples and comparative examples of the present invention, the temperature distribution and the amount of sublimation of raw materials were determined by simulation for the silicon carbide single crystal growth apparatus shown in FIG. Depending on the examples or comparative examples, a heat transfer member having a shape different from that of the heat transfer member 7 shown in FIG. 1 may be used.
Crystal growth analysis software "Virtual Factor" (manufactured by STR-Group Ltd) was used for the simulation. This simulation software is widely used for simulating temperature distribution, raw material sublimation, and crystal growth in the growth of silicon carbide single crystals by the sublimation recrystallization method.

The crystal growth steps based on the crystal growth simulations in this example and the comparative example are as follows.
That is, the method for growing a silicon carbide single crystal includes a step of crystal growing a single crystal from the seed crystal 8 installed in the seed crystal setting unit 3. Since the single crystal is filled in the raw material filling portion 2, the sublimated raw material gas is recrystallized on the surface of the seed crystal 8 to grow. The silicon carbide raw material sublimates the silicon carbide raw material by supplying electric power to the work coil 5 provided outside the crucible main body 1 and inducing and heating the crucible main body 1 at a high frequency. The sublimated raw material gas rises in the crucible and is supplied toward the seed crystal 6. The output of the work coil 5 at this time is set so that the maximum temperature of the raw material filled in the raw material filling portion is at least 2300 ° C. or higher. The outer region of the crucible is filled with Ar gas, and the Ar partial pressure is controlled to 10,000 Pa or less to grow a silicon carbide single crystal.

In this example and the comparative example, a simulation was carried out in which the above-mentioned silicon carbide single crystal growth was carried out for 50 hours.

(Example 1)
In Example 1, as shown in FIG. 1, a simulation was performed on a single crystal growth apparatus in which a perforated disk-shaped heat transfer member 7 was arranged inside the raw material 8 filled in the raw material filling portion 2. The details of the conditions are shown below.
Inner radius of crucible body 1: 120 mm
Filling height of raw material in raw material filling part 2: 125 mm
Distance from the upper surface of the raw material in the raw material filling portion 2 to the lower end of the seed crystal: 119 mm
Raw material 10 in raw material filling part 2: Silicon carbide powder Material of heat transfer member 7: Graphite Thermal conductivity of heat transfer member 7: Approximately 40 W / mK (at 2000 ° C)
Shape of heat transfer member 7: Perforated disk with inner radius of 10 mm, outer radius of 80 mm, thickness of 5 mm Horizontal position of heat transfer member 7: So that the central axis of the heat transfer member 9 coincides with the central axis of the pit body 1. Position in the vertical direction of the heat transfer member 7: The lower end of the heat transfer member 7 coincides with the height at which the distance from the bottom surface of the radius body 1 is 0.5 times the raw material filling height in the raw material filling portion 2. set on

In this simulation, the output of the work coil 5 is adjusted so that the maximum temperature in the raw material (near the inner wall of the crucible) reaches 2460 ° C., and the crucible body 1 is heated. Growth was started and a 50-hour crystal growth simulation was performed.

In this example, the temperature distribution simulation and the crystal growth simulation at each growth time were carried out for the silicon carbide single crystal growth for 50 hours using the above conditions. During the crystal growth simulation, the temperature was not controlled by changing the movement or arrangement of the crucible body 1 and other members, or changing the output of the work coil 5. The porosity of the raw material in the raw material filling portion at the start of the simulation was set to 80%.

As a result of temperature distribution simulation, in the raw material filling part, the height direction is the center height in the thickness direction of the heat transfer member, and the radial direction is the position of the central axis of the pit body. It was confirmed that the temperature rise of 4 ° C. was confirmed by using the heat transfer member as compared with the case where the heat transfer member was not used (Table 1). Here, the filling height of the raw material in the raw material filling portion when the heat transfer member is not used is made to match the filling height of the raw material when the heat transfer member is used. In the following Examples and Comparative Examples, the positions in the raw material filling section for evaluating the temperature rise are the same as those in Example 1.

As a result of the crystal growth simulation, the sublimation amount of the silicon carbide raw material increased by 17% after 50 hours of growth as compared with the case where the heat transfer member was not used (Table 1).
FIG. 2 shows the distribution of porosity in the cross section of the region filled with the raw material in the raw material filling portion at the time point after 50 hours of growth by the simulation of Example 1. FIG. 3 shows the distribution of porosity after 50-hour growth when crystal growth is performed without using a heat transfer member for comparison. Here, for example, the numerical value "0.2" in the figure indicates that the porosity is 20%. In the simulations of FIGS. 2 and 3, the filling heights of the raw materials in the raw material filling section were matched. In the first embodiment, there may be a region having a large porosity not only in the vicinity of the side wall of the crucible where sublimation of the raw material is likely to occur by the conventional method, but also in the upper region, the opening region and the region below the heat transfer member. Recognize. Due to the temperature rise near the center of the raw material filling part and the change in the porosity distribution by the temperature simulation, heat is supplied to the central axis side in the raw material filling part by the heat transfer member to promote the sublimation of the silicon carbide raw material. It can be seen that the silicon carbide raw material in the filling portion can be used more efficiently.
In FIGS. 2 and 3, the region where the porosity is smaller than the porosity of 0.8 at the start of the simulation is a region where the temperature is low before the sublimation gas generated inside the raw material filling portion goes out. It is considered that this is a region where the porosity is lowered due to the passage and the precipitation of polycrystals here.

(Example 2)
In Example 2, instead of the heat transfer member of Example 1 shown in FIG. 1, a heat transfer member made of disc-shaped graphite having a thickness of 5 mm, an inner radius of 20 mm, and an outer radius of 60 mm was used. The heat transfer member was arranged so that the lower end of the heat transfer member coincided with the height at which the distance from the bottom surface of the crucible body 1 was 0.7 times the height of the raw material filling portion. Other than that, the simulation was performed in the same manner as in Example 1.

As a result of temperature distribution simulation, it was confirmed that the temperature rose by 1 ° C. due to the use of the above heat transfer member (Table 1). As a result of the crystal growth simulation, it can be seen that the sublimation amount increased by 22% as compared with the case where the heat transfer member was not used (Table 1), and the sublimation of the silicon carbide raw material by the use of the heat transfer member was made more efficient. In this embodiment, since the heat transfer member spreads in the horizontal direction is small, the temperature rise near the central axis is small, but even when the heat transfer member acts locally on the temperature distribution in the entire crucible, the silicon carbide raw material is used. The effect of promoting sublimation is recognized.

(Example 3)
In Example 3, the simulation was performed in the same manner as in Example 1 except that a heat transfer member made of tungsten having the same shape was used instead of the heat transfer member of Example 2. The thermal conductivity of tungsten is 104 W / mK at 2000 ° C.

As a result of temperature distribution simulation, it was confirmed that the temperature rose by 2 ° C. due to the use of the above heat transfer member (Table 1). As a result of the crystal growth simulation, it can be seen that the amount of sublimation increased by 21% as compared with the case where the heat transfer member was not used (Table 1), and the sublimation of the silicon carbide raw material by the use of the heat transfer member was made more efficient.

(Example 4)
In the fourth embodiment, the annular heat transfer member 7 shown in the cross-sectional view in FIG. 4 was used instead of the heat transfer member of the first embodiment. The annular heat transfer member 7 has an inner radius of 25 mm and an outer radius of 55 mm. Further, the heat transfer member 7 was arranged so that the center height of the cross-sectional circle of the heat transfer member 7 coincided with the height at which the distance from the bottom surface of the crucible was 0.5 times the raw material filling height. Other than that, the simulation was performed in the same manner as in Example 1.

As a result of temperature distribution simulation, it was confirmed that the temperature rose by 4 ° C. due to the use of the above heat transfer member (Table 1). As a result of the crystal growth simulation, it can be seen that the amount of sublimation increased by 15% as compared with the case where the heat transfer member was not used (Table 1), and the sublimation of the raw material of silicon carbide by the use of the heat transfer member was made more efficient.

(Example 5)
In Example 5, instead of the heat transfer member of Example 1, a cylindrical heat transfer member 7 made of tungsten shown in the cross-sectional view of FIG. 5 was used. The cylindrical heat transfer member 7 has an inner radius of 20 mm, an outer radius of 25 mm, and a height of 55 mm. The heat transfer member 7 was arranged so that the lower end of the heat transfer member 7 coincided with the height at which the distance from the bottom surface of the crucible body 1 was 0.4 times the raw material filling height. Other than that, the simulation was performed in the same manner as in Example 1.

As a result of temperature distribution simulation, it was confirmed that the temperature rose by 1 ° C. due to the use of the above heat transfer member (Table 1). As a result of the crystal growth simulation, it can be seen that the amount of sublimation increased by 17% as compared with the case where the heat transfer member was not used (Table 1), and the sublimation of the silicon carbide raw material by the introduction of the heat transfer member was made more efficient.

(Example 6)
In Example 6, instead of the heat transfer member of Example 1, two cylindrical heat transfer members made of tungsten shown in the cross-sectional view of FIG. 6 were used. One (7a) of the cylindrical heat transfer member has an inner radius of 20 mm, an inner radius of 25 mm and a height of 55 mm, and the other (7b) has an inner radius of 50 mm, an outer radius of 55 mm and a height of 55 mm. The central axes of the two heat transfer members 7a and 7b coincide with the central axis of the crucible body 1, and both are transmitted to a height at which the distance from the bottom surface of the crucible body 1 is 0.2 times the raw material filling height. The thermal members were arranged so that the lower ends of the members coincided with each other. Other than that, the simulation was performed in the same manner as in Example 1.

As a result of temperature distribution simulation, it was confirmed that the temperature rose by 3 ° C. due to the use of the above heat transfer member (Table 1). In addition, as a result of the crystal growth simulation, the amount of sublimation increased by 15% as compared with the case where the heat transfer member was not used (Table 1), and the sublimation of the silicon carbide raw material by using the heat transfer member was made more efficient. Recognize.

(Comparative Example 1)
Same as Example 1 except that the heat transfer member having the same outer radius and inner radius difference (inner radius 50 mm, outer radius 120 mm) and thickness as the heat transfer member used in Example 1 contacts the inner side wall of the crucible body. And simulated.
As a result of temperature distribution simulation, it was confirmed that the temperature rose by 4 ° C. due to the use of the above heat transfer member (Table 1).
In addition, as a result of the crystal growth simulation, the rate of increase in the amount of sublimation was only 1% as compared with the case where the heat transfer member was not used (Table 1).

In Comparative Example 1, since the outer circumference of the heat transfer member is in contact with the inner wall of the crucible body, the flow of the sublimated gas sublimated under the heat transfer member is obstructed. As a result, polycrystals are deposited on the lower part of the heat transfer member (confirmed by actual growth), and the amount of sublimation is reduced. In addition, since the heat transfer member is in contact with the wall of the crucible body, it is considered that the sublimation amount is reduced because the escape route of the sublimation gas is partially blocked.

(Comparative Example 2)
For comparison with Example 1, the heat transfer member has the same outer radius and thickness as the heat transfer member used in Example 1, but has a disk shape without a hole in the center (that is, a disk having an outer radius of 70 mm). The simulation was performed in the same manner as in Example 1 except that the thermal member was used.
As a result of temperature distribution simulation, it was confirmed that the temperature rose by 4 ° C. due to the use of the above heat transfer member (Table 1).
In addition, as a result of the crystal growth simulation, the rate of increase in the amount of sublimation was -3% (decrease in the amount of sublimation) as compared with the case where the heat transfer member was not used, and no effect was observed (Table 1).

In Comparative Example 2, as in the case of Comparative Example 1, the precipitation of polycrystals was observed on the lower side of the heat transfer member, and the amount of sublimation was reduced. In the case of Comparative Example 2, since the heat transfer member has no opening, it is considered that the cause of the decrease in the amount of sublimation is that the escape route of the sublimation gas passing through the lower part of the heat transfer member is blocked at the center of the crucible body. Be done.

(Examples 7 to 8, Comparative Example 3)
With reference to the simulation results of Example 1, Comparative Example 1, and Comparative Example 2, the shape of the heat transfer member was changed as follows in order to confirm the influence of the horizontal position and structure of the heat transfer member on the effect. Performed a simulation in the same manner as in Example 1.
That is, the inner radius of the heat transfer member having the same difference and thickness as the heat transfer member used in Example 1 is changed, and the inner radius of Comparative Example 1 and Comparative Example 2 is maximum (50 mm). In the case of the minimum (0 mm, no opening), the simulation was performed in increments of 10 mm between them. When the inner radius is 10 mm, it is the first embodiment.
Under the above conditions, the case where the inner radius is 20 mm is referred to as Example 7, the case where the inner radius is 30 mm is referred to as Example 8, and the case where the inner radius is 40 mm is referred to as Comparative Example 3. Table 1 shows the simulation results of the temperature rise and the rate of increase in the amount of sublimation when the heat transfer member is not used.
Further, FIG. 7 shows a change in the rate of increase in the amount of sublimation of the silicon carbide raw material with respect to the inner radius of the heat transfer member. It can be seen that the amount of sublimation of the silicon carbide raw material is greatly increased in the range of the inner radius of 10 to 30 mm. On the other hand, when the outer radius of the heat transfer member is large and close to the side wall of the crucible as in Comparative Examples 2 and 3, the outer radius of the heat transfer member is small and the inner radius is 0 mm (without an opening) as in Comparative Example 1. In this case, the rate of increase in the amount of sublimation of the raw material is small or conversely decreases, and it can be seen that efficient sublimation of the silicon carbide raw material has not been achieved.

The method for producing a silicon carbide single crystal having a heat transfer member in the raw material of the present invention can be used for producing a silicon carbide single crystal having a particularly large diameter and a long length.

1 ... Crucible body, 2 ... Raw material filling part, 3 ... Seed crystal support part, 4 ... Insulation material, 5 ... Work coil, 6 ... Seed crystal, 7 ... Transmission Thermal parts, 8 ... Raw materials

Claims (8)

Using a single crystal growth apparatus having a graphite-made pit body, a raw material filling portion located at the lower part of the pit main body, and a seed crystal support portion in which a seed crystal is installed at a position facing the raw material filling portion. A method for producing a silicon carbide single crystal by a sublimation recrystallization method in which a sublimation gas generated by heating a silicon carbide raw material filled in a raw material filling portion is recrystallized on a silicon carbide seed crystal installed on the seed crystal support portion. And
The crucible body has a cylindrical inner wall surface and has a cylindrical inner wall surface.
An annular heat transfer member made of a substance having a higher thermal conductivity than the silicon carbide raw material is arranged inside the silicon carbide raw material.
The heat transfer member is arranged in a region where the distance from the central axis of the crucible body is 5 mm or more and 0.85 times or less of the inner radius of the crucible body .
The thermal conductivity of the heat transfer member is 30 W / mK or more at a temperature of 2000 ° C. or more.
A method for producing a silicon carbide single crystal, wherein the heat transfer member is made of tungsten. Using a single crystal growth apparatus having a graphite-made pit body, a raw material filling portion located at the lower part of the pit main body, and a seed crystal support portion in which a seed crystal is installed at a position facing the raw material filling portion. A method for producing a silicon carbide single crystal by a sublimation recrystallization method in which a sublimation gas generated by heating a silicon carbide raw material filled in a raw material filling portion is recrystallized on a silicon carbide seed crystal installed on the seed crystal support portion. And
The crucible body has a cylindrical inner wall surface and has a cylindrical inner wall surface.
An annular heat transfer member made of a substance having a higher thermal conductivity than the silicon carbide raw material is arranged inside the silicon carbide raw material.
The heat transfer member is arranged in a region where the distance from the central axis of the crucible body is 5 mm or more and 0.85 times or less of the inner radius of the crucible body .
The thermal conductivity of the heat transfer member is 30 W / mK or more at a temperature of 2000 ° C. or more.
The shape of the heat transfer member is axisymmetric, and the heat transfer member is arranged so that the central axis of the heat transfer member coincides with the central axis of the crucible body.
The shape of the heat transfer member is a perforated disk-like shape having a rectangular cross section when cut in a plane passing through the central axis of the heat transfer member and a length in the radial direction longer than the length in the axial direction. A method for producing a silicon single crystal. Using a single crystal growth apparatus having a graphite-made pit body, a raw material filling portion located at the lower part of the pit main body, and a seed crystal support portion in which a seed crystal is installed at a position facing the raw material filling portion. A method for producing a silicon carbide single crystal by a sublimation recrystallization method in which a sublimation gas generated by heating a silicon carbide raw material filled in a raw material filling portion is recrystallized on a silicon carbide seed crystal installed on the seed crystal support portion. And
The crucible body has a cylindrical inner wall surface and has a cylindrical inner wall surface.
An annular heat transfer member made of a substance having a higher thermal conductivity than the silicon carbide raw material is arranged inside the silicon carbide raw material.
The heat transfer member is arranged in a region where the distance from the central axis of the crucible body is 5 mm or more and 0.85 times or less of the inner radius of the crucible body .
The thermal conductivity of the heat transfer member is 30 W / mK or more at a temperature of 2000 ° C. or more.
The shape of the heat transfer member is axisymmetric, and the heat transfer member is arranged so that the central axis of the heat transfer member coincides with the central axis of the crucible body.
Manufacture of a silicon carbide single crystal in which the shape of the heat transfer member is similar to an annular shape having a circular cross section or an elliptical annular shape when cut in a plane passing through the central axis of the heat transfer member. Method. Method for producing a silicon carbide single crystal according to claim 2 or 3 consisting of the heat transfer member backlash tungsten. The method for producing a silicon carbide single crystal according to any one of claims 1 to 4, wherein the heat transfer member has an inner radius of 10 to 30 mm. The method for producing a silicon carbide single crystal according to any one of claims 1 to 5, wherein a plurality of the heat transfer members are arranged inside the silicon carbide raw material. The method for producing a silicon carbide single crystal according to claim 6, wherein the plurality of heat transfer members are arranged side by side in the vertical direction with their respective central axes aligned with the central axis of the crucible body. The method for producing a silicon carbide single crystal according to claim 6, wherein a plurality of the heat transfer members having different structures are arranged at different positions in a horizontal plane without contacting each other.

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